Combined IR-RF combat identification friend-or-foe (IFF) system for the dismounted soldier

ABSTRACT

Combined IR-RF combat identification friend-or-foe (IFF) system for the dismounted soldier comprising IR-RF interrogator mounted on a small arms and IR-RF transponder mounted on a friendly target, wherein sharp-diagram K-band RF channel provides brief information about friendly targets that could be in attacked area, and if they are, develop alert signal: “Friendly soldiers are in the area”. IR channel of the system prevents friendly fire in the case of direct sighting to a friendly soldier.

DESCRIPTION OF THE RELATED ART

The present invention is the continuation of the U.S. patent application Ser. No. 11/685,682 filed Mar. 13, 2007 by the authors of the present invention.

FIELD OF THE INVENTION

This invention relates generally to combat identification systems for the dismounted soldier and more particularly to a secure covert identification as friend or foe (IFF) system for interrogating a dismounted soldier with a coded infrared (IR) and radio (RF) signals, which are received and encoded by the target that sends combined response signal to prevent a friendly fire.

The Dismounted Armed Forces have an interest in the remote identification of a person as friend or foe, particularly to prevent friendly fire in armed conflicts. Identification as friend or foe (IFF) systems are well-known for decades for military aircraft. Such systems are based on RF transmission and very useful for preventing action against friendly aircrafts.

The military platform commanders target friend-or-foe identification presents a difficult decision for a military platform commander, who must decide whether to engage a detected target while avoiding accidental fratricide.

This problem is even more difficult for the dismounted soldier who may be moving covertly through an unknown combat zone at night with a limited visibility. U.S. Pat. No. 4,851,849 issued to Otto Albersdoerfer describes a typical active IFF RF technique for a military vehicle, which is equipped with a RF transponder that emits a coded return signal when an interrogating radar pulse is detected by its receiver.

U.S. Pat. No. 5,686,722 issued to Dobois et al. describes an active optical IFF technique for vehicles uses a selective wavelength optical coding system with tunable optical beacons mounted on each vehicle.

Also, U.S. Pat. No. 5,966,226 issued to Gerber describes an active combat IFF system for a dismounted soldier that includes a weapon-mounted laser transmitter for interrogating suspected targets and a harness including means for receiving the interrogatory signal and means for responding with an encoded radio, acoustic or optical signal.

Therefore, all mentioned and similar IFF systems utilize all-optical, all-radio or combined solutions, where the combined ones use an optical interrogating signal and RF response signal.

All these systems have obvious disadvantages that could be critical in battlefield conditions. An optical interrogator has a sharp beam providing secure covert identification, but can reach the target only when the line laser transmitter—optical detector mounted on the friendly target is not shaded by any objects, such as leafs, woods, walls, etc. Unlike optical signal, RF one passes through the objects, which are not transparent for optical signals, but RF interrogator has very wide diagram because it has thousands times longer wavelength than optical signal. Therefore, the RF antenna with 30-mm aperture has the transmitting/receiving diagram of 37 arc degrees at 8-mm RF wavelength (Ka band). Such wide diagram does not allow recognizing each individual soldier; and the response signal comes from such large area too.

The attempts to make a combined system utilizing optical interrogator and RF response unit cannot provide solution because such system inherits the disadvantages of optical and RF systems. Here, optical signal can be shaded by some not-transparent objects and RF response can be received from a number of response units simultaneously.

There are two distinctive situations on a battlefield:

-   -   Sightline is not shaded, so all-optical IFF system works.     -   Sightline is obstructed, or somebody, probably enemy soldiers         are hiding in trees, behind a fence, inside a building, etc. In         this case all-optical IFF system is useless. RF system works and         can provide general warning, if some friendly soldiers are         there.

These situations are illustrated on FIG. 1. In the case B (see FIG. 1) RF response signal shows that some friendly soldiers are behind a fence and tells the shooter to not open a chaotic fire towards direction.

Therefore, only combination of two independent channels, IR optical and RF one, can allow identifying friendly soldiers in these both cases. Here, in the second case, a shooter uses RF channel only that can give him information about a presence of some friendly soldiers in 37-arc degree sector directed along the sightline; it can prevent a chaotic fire that is very often in such situation.

In the first case, when the sightline is not obstructed, a shooter uses IR optical channel that allows precisely identifying each friendly soldier.

In some cases, all channels may be used, where the RF one provides brief information about possible presence of friendly soldiers is the suspicious sector and, after this IR optical channel is used.

DESCRIPTION OF THE ART PROPOSED IN THE U.S. patent application Ser. No. 11/685,682 FILED BY THE AUTHORS OF THE PRESENT INVENTION

The present invention is the continuation of the art proposed in the U.S. patent application Ser. No. 11/685,682 filed Mar. 13, 2007 by the authors of the present invention.

The IR IFF system described in the U.S. patent application Ser. No. 11/685,682 consists of two separate units—the request one mounted on small arms and the response one mounted on a helmet of soldier. The laser transmitter of the request unit installed on a rifle emits a sharp beam that is wide enough to illuminate the optical receiver(s) mounted on the helmet or uniform of the soldier. When this optical signal is received by the response unit, the unit sends a coded optical response signal to the request unit; this signal that reaches the request unit and, being decoded, activates the simple optical alarm signal telling the shooter that “it is a friendly target”. Also, the optical signal received by the response unit simultaneously activates a distinctive sound signal (sounded by a headphone or buzzer) informing the soldier that “he could be under a friendly fire”. This embodiment proposes the laser beam with divergence of 4 milliradians that illuminates the circle of 2-meter diameter at 500-meter distance. Such beam divergence is close to the optimal one, because a wider beam could illuminate several targets simultaneously causing inappropriate responses, and, also, diminishing the security of this system, but a very narrow beam (proposed in some mentioned above patents), in many cases, could miss the sensor, especially at short distances, so IFF detection will fail.

Proposed in this embodiment IR radiation emitted by lasers of the units has wavelength of 1550 nm that is the standard for fiber-optical (FO) telecommunication lines. So, such telecommunication laser transmitters, receivers and associated electronics are very well developed, inexpensive and widely available on the market. Moreover, the radiation of these wavelengths is safe to the human eye, because, unlike the wavelength shorter than 1000 nm, it is not transparent for human eye, so it can not be focused on the retina.

The response unit described in the U.S. patent application Ser. No. 11/685,682 is comprised of an optical assembly consisting of a number of separated receiving-transmitting optical units attached to the belt of harness, or built in specially designed helmet, wherein each of them contains optical receiver and transmitting laser diode (LD) equipped with receiving and transmitting lenses. These optical units are electrically connected to the electronic processing unit that detects the direction of received signal, decodes it and develops a response one. Therefore, the response unit of this embodiment sends an optical response signal towards the sector from which it receives the request signal.

SUMMARY OF THE INVENTION

The present invention is based on the art described in the U.S. patent application Ser. No. 11/685,682 and solves the above-described problems by providing a combined IR-RF system, which can be used in both combat situations: when the sightline is not shaded and when the sightline is obstructed.

THE DRAWINGS

FIG. 1 illustrates cases of operation of IFF system of the preferred embodiment of the present invention in battlefield conditions.

FIG. 2 depicts the schematic diagram of IFF system of the preferred embodiment.

FIG. 3 depicts the block diagram of the RF interrogator of the preferred embodiment.

FIG. 4 depicts the block diagram of the RF transponder of the preferred embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION-IR-RF COMBINED IFF SYSTEM

The schematic diagram of IFF system of the present invention is depicted in FIG. 2. It includes two independent channels: IR optical channel—the object of the invention described in the U.S. patent application Ser. No. 11/685,682—and the additional RF one. Each channel includes a weapon-mounted IFF interrogatory unit for each soldier and active helmet-mounted identification as a friend or foe (IFF) response unit. Infrared (IR) channels are employed in both units—the request and response ones—as described in the U.S. patent application Ser. No. 11/685,682.

The additional RF channel utilizes the short-wavelength (Ka band) RF signal that allows emitting RF signal in a relatively narrow (for small 30-mm-aperture antenna) sector of 37 arc degrees directed along the sightline. The hardware of Ka-band RF channel is well-developed, has a small size and weight, and inexpensive.

The request unit contains the IR transmitting/receiving optical unit equipped with short fiber-optic line 4 and lens 1, RF transmitting/receiving antenna 2, electronic block 3 and alert light 5.

The response unit contains the set of optical receiving/transmitting blocks 6, RF receiving/transmitting antenna 7, electronic block 8 and alert buzzer 9.

DETAILED DESCRIPTION OF RF CHANNEL OF THE REQUEST UNIT Interrogator

The detailed block diagram of RF request channel is depicted in FIG. 3. The single electronic block, which is common for both—IR (positions 1 and 2 on FIG. 3) and RF—channels, contains microprocessor 8, flush memory 9, USB port 10, alert LED 14 and switch 13. It develops coded request signals, decodes input response signal and activates alert LED 14. To separate the alert signals coming from IR and RF channels, the LED 14 can blink when it is activated by the RF signal, or change color to yellow, for example.

The RF channel uses the RF transponder, which consists of receiving and transmitting channels. The transmitting channel contains pre-amplifier-modulator 7 and power amplifier 5 feeding antenna 3 via input/output switch 4. The receiving channel contains detector-amplifier-former 6 that detects (demodulates), amplifies and fixes shape of digital RF signals coming from transmitting/receiving antenna 3 via switch 4. Pre-amplifier-modulator 7 modulates and amplifies the digital electric signals developed by processor 8. Power amplifier 5 provides necessary power of output signal that is transmitted to the response unit via antenna 3. Received by antenna 3 RF response signal is demodulated and pre-amplified by detector-amplifier-former 6 that, also, standardizes digital output signal entering processor 8. Because the RF transponder uses single antenna 3 for transmitting and receiving, it utilizes RF switch 4 to change modes from transmitting to receiving one and wise versa. The switch 4 is controlled by processor 8.

RF transponder of the present invention utilizes Ka-waveband. The hardware of this waveband is well-developed (particularly, for satellite communication) and inexpensive.

DETAILED DESCRIPTION OF RF CHANNEL OF THE RESPONSE UNIT

The detailed block diagram of RF channel of the response unit is depicted in FIG. 4. The RF channel of the response unit contains the blocks that are similar to the ones of the request unit. The only difference is antenna 3, which has wide diagram that covers hemisphere so providing single response for all request signals coming from any direction. The multi-channel IR unit of the response unit is described in details in the U.S. patent application Ser. No. 11/685,682.

The response unit contains single electronic block, which is common for both—IR (positions 1 and 2 on FIG. 4) and RF—channels, consisting of microprocessor 8, flush memory 9, USB port 10, alert buzzer 14 and switch 13. It processes an input request signal, activates alert buzzer 14 and develops coded request signals. To separate the alert signals coming from IR and RF channels, the buzzer 14 can sound by short signals if it is activated by the RF signal, or change tone of the sound, for example.

The RF channel, which is similar to one of the request signal, uses the RF transponder, which consists of receiving and transmitting channels.

The transmitting channel contains the pre-amplifier-modulator 7 and power amplifier 5 feeding antenna 3 via input/output switch 4.

The receiving channel contains detector-amplifier-former 6 that detects (demodulates), amplifies and fixes shape of digital RF signals coming from transmitting/receiving antenna 3 via switch 4. The pre-amplifier-modulator 7 modulates and amplifies the digital electric signals developed by processor 8. The power amplifier 5 provides necessary power of output signal that is transmitted to the response unit via antenna 3. Received by antenna 3 RF response signal is demodulated and pre-amplified by the detector-amplifier-former 6 that, also, standardizes the digital output signal entering processor 8. Because the RF transponder uses a single antenna 3 for transmitting and receiving, it utilizes the RF switch 4 to change modes from transmitting to receiving one and vise versa. The switch 4 is controlled by processor 8.

To prevent a false alert, the request and response signals utilize different frequencies, wherein the response RF signal is in compliance with STANAG4579 standard. Such solution additionally allows monitoring battlefield situation. Also, the request and response signals are shifted in time in such a way when the response signal is delayed against the request one for a specific time—a portion of millisecond. It means that the request unit switches to the receiving channel only after this specific time and holds it on for a short time period of a portion of millisecond—the time that is necessary to receive the response signal. Thus, it allows the system rejecting the RF signals coming from other sources.

The request signal, also, activates IR channel, which becomes active for a short period of time—the time that is necessary for optical signal to exchange between the response and request units. This solution allows the response unit saving energy of the power supply.

Therefore, the system works as follows:

The request unit sends RF signal towards the area to which the sightline is directed. It activates the response units of friendly soldiers that are in this area. These units send response RF signals, which are received by the request unit of the shooter and give to him alert signal: “Friendly soldiers are in the area”. Simultaneously, the request signal activates IR channels of the response units of these friendly soldiers. So, if the shooter continues operation and directly targets any of these friendly soldiers, the IR channel of the targeted soldier sends IR response signal so preventing friendly fire. If the shooter cancels the operation, IR channels of the response units of these soldiers become automatically inactivated after a short period of time; and only receivers of RF channels still working in waiting mode. 

1. An identification friend or foe system for military small arms to determine whether a target that has been selected is a friendly target comprising: a request unit containing IR signal source attached to said small arms and arranged to radiate encrypted request signals, a IR detection system attached to said small arms that receives a IR response signal and a visual alert sign mounted on the sight of said small arms that is activated by said received response signal, a response unit containing IR detection system attached to a friendly target that receives said IR request signal, a IR signal source attached to a friendly target and arranged to radiate said IR response signals, and a sound alert buzzer mounted on said friendly target and activated by said received request signal, wherein the improvement comprises: said request unit is additionally equipped with a RF interrogator that comprises a sharp-diagram RF transmitter mounted on a sight of said small arm, which sends encrypted RF request signal in area to which sightline of said small arm is directed, and a RF receiver receiving encrypted RF response signal emitted by said friendly targets that are in said area, said response unit is additionally equipped with RF transponder attached to said friendly target that comprises RF receiver, which receives encrypted RF request signal emitted by said interrogator, and a RF transmitter transmitting the encrypted RF response signal back to said RF interrogator, wherein received RF request signal also activates IR cannel of said response unit so saving energy of power supply of said response unit.
 2. The identification friend or foe system of claim 1, wherein the RF interrogator of claim 1 comprises: a RF K-band sharp-diagram transmitting/receiving antenna mounted on the small arms and connected to a RF switch that switches modes from transmitting to receiving one, an RF electronic unit mounted in convenient place of the small arm containing transmitting and receiving RF channels, which are switched by said switch, a single electronic microprocessor block controlling IR and RF channels of the request unit of claim 1, which develops coded request signal, processes input RF and IR response signals and activates the visual alert sign of claim
 1. 3. The identification friend or foe system of claim 1, wherein the RF transponder of claim 1 comprises: a RF K-band unidirectional-diagram transmitting/receiving antenna mounted in any convenient place of the friendly target and connected to a RF switch that switches modes from transmitting to receiving one, an RF electronic unit mounted in any convenient place of the friendly target and containing transmitting and receiving RF channels, which are switched by said switch, a single electronic microprocessor block controlling IR and RF channels of the response unit of claim 1, which processes input RF and IR request signals, develops coded response signal, and activates the alert buzzer of claim
 1. 4. The identification friend or foe system of claim 1, wherein RF response signal is delayed about RF request signal for a specific time period of a portion of millisecond that allows selecting the RF response signals of claim 1 from RF signals emitted by other sources.
 5. The identification friend or foe system of claim 1, wherein RF response signal has different frequency then RF request signal that allows selecting the RF response signals of claim 1 from RF signals emitted by other sources, wherein said frequency is in compliancy with STANAG4579 standard that additionally allows monitoring battlefield situation.
 6. The identification friend or foe system of claim 1, wherein RF signal emitted by the transponder of claim 1 contains ID of the friendly target; so these signals received by interrogator of claim 1 allow evaluating situation in attacked area. 